Strip-tensioning means for sewing machines



Oct. 10, 1939.

c. s. THOMPSON ET AL 9 STRIP-TENSIONING MEANS FOR SEWING MACHINES Filed Nov. 6, 1937 2 Sheets-Sheet l ,HZber'Z S. Riviera BY Owu W ATTORNEY 1939. c. s THOMPSON Er AL 2,175,494

STRIP-TENSIONING MEANS FOR SEWING MACHINES Filed Nov. 6, 1937 2 Sheets-Sheet 2 INVENTORS:

Charles 51 Thompson, Frankfilfpqera & E fllberb Sflwzere,

ATTORNEYS.

Patented Oct. 10, 1939 UNITED STATES PATENT OFFlCE STRIP-TENSIONING MEANS FOR SEWING MACHINES Application November 6, 1937, Serial No. 173,078

8 Claims.

This invention relates to means useful more particularly with sewing machines, for maintaining binding or edging strips under tension as they are passed to the stitch-forming instrumentalities of such machines for attachment to the edges of the body fabrics of garments, etc.

The chief aim of our invention is to make it possible to maintain a binding strip uniformly taut and under a predeterminable degree of conlO stant tension, so that upon relaxation of the strip after it is secured to the body fabric, a smooth and undistorted edge finish is assured. This desideratum we attain as hereinafter more fully disclosed through provision of a tensioning unit wherein the tensioning function is shared by a main tensioning element and a supplemental tensioning element through which the strip is horizontally passed in succession in upright position and both of which are accessible from above for convenience of ready insertion of the strip initially, said main tensioning element including a pair of opposing clamp members subject to regulatable spring pressure, and said supplemental element being in the form of an upright double-timed rotatably-adjustable fork which is spaced from said main device and supported by one of the component members of the latter.

In connection with strip tensioning means characterized as above, we further aim to provide simple and reliable means for controlling the clamp members of the main tensioning element so that the tension on the strip may be relieved when desired or required without necessitating stoppage or slowing down of the sewing machine.

Additional objects and advantages of our invention will appear from the following detailed description of the attached drawings, wherein Fig. I shows in side elevation, a sewing machine with strip tensioning means conveniently embodying the present improvements.

Fig. II shows the organization in plan, with the needle arm of the sewing machine broken away.

Fig. III is a fragmentary sectional view taken as indicated by the arrows III-III in Figs. I and II and drawn to a larger scale to more clearly show the details of our improved strip tensioning means; and

Fig. IV is a perspective view of a guide element 5C which forms a part of the strip tensioning means.

The sewing machine herein illustrated is of a well known flat bed type suitable for securing a binding strip to the edge of a body fabric B, the

machine having two needles N and N, a looper 55 L and a cover thread laying finger L which cooperate in forming a double chain stitch seam such as conventionallyv indicated at C in Fig. II to se cure the strip as the body fabric is intermittently advanced across the work plate P of the machine by the feed dog indicated in dotted lines 6 at D in Fig. II. As shown, the strip S is passed horizontaliy along the front side of the machine in upright position and traverses a suitably-supported folder F whereby it is doubled longitudinally. The illustrated folder may be of the con--10 struction disclosed in a copending application, Serial Number 67,028 filed by us on March 4, 1936, by which the strip S is delivered around the edge of the body fabric B immediately in advance of the needles N, N of the sewing machine, with its fold margins lying perfectly flat against the opposite faces of said fabric.

The strip tensioning means which constitutes the subject of our present invention is comprehensively designated by the numeral I in Figs. 20 1-111 of the drawings. As shown it includes a main tensioning element formed by a pair of vertically-arranged clamp plates 2 and 3 between which the strip S passes enroute to the folder F and the stitch-forming instrumentalities of the 25 seewing machine. The plate 2, it will be noted, extends well below the plate 3 and is secured near its lower edge to the front side of the sewing machine frame by a pair of screws 4. Projecting outwardly from the center of the movable clamp 30 member 3 is a headed stud 5 whereof the shank loosely fits the notch 6 at the upper end of a vertical supporting arm I so that said plate is free to adapt itself to the fixed clamp plate 2. At its lower end, the arm 1 loosely engages the shank 35 of a headed screw stud 8 which is threaded axially into the head of a screw stud 9 which is in turn threaded into the lower part of the clamp plate 2. By virtue of this arrangement, the arm 1 is supported by the screw stud 8 with capacity 40 for universal movement. The clamp member 3 is held against rotation about the axis of the stud 5 by a projecting stud l0 thereon which extends through a hole of slightly larger diameter in said arm. At its mid-point, the arm I has an out- 45 wardly-projecting boss II which is axially apertured to clear a guide stem projecting forwardly from the fixed clamp plate 2. Interposed between the arm I and a finger nut l3 at the outer threaded end of the stem I2 is a helical compression spring l5 by action of which the movable clamp member 3 is yieldingly urged toward the fixed clamp member 2 to impose frictional restraint upon the binding strip S. By adjusting the finger nut I3, the pressure of the spring i5 may be increased or decreased to vary the drag imposed on the strip S, and the tensioning device adapted for operation upon binding strips of different textures and characteristics. The jam nut shown at l6 serves to secure the finger nut l3 against accidental displacement after adjustment. In order that the strip S may be relieved of tension when desired or required, there is provided a curved finger H with a cam bevel l8 at its free end adapted to coact with a rounded lug projection l9 at the back of the arm 1, said finger being fulcrumed to swing on the stud 9 as an axis. Thus when the finger I I is moved counter-clockwise in Fig. I, its cam bevel l8 encounters the lug projection is on the arm 1, with the result that the clamp member 3 is moved away from the clamp member 2 in opposition to the force of the spring l5. Normally the finger I1 is held in its inactive position shown in Fig. I by a tension spring 20, with the tail projection 2| thereof against a fixed stop 22 on the plate 2. The tension release finger I I may be operated by any suitable means, for example, through a wire connecting link 23, by a foot treadle or any lever, not illustrated, the movement of said finger being limited by another fixed stop 24 on the clamp plate 2.

Disposed substantially in the plane of meeting of the plate components 2 and 3 of the main ten sioning element and supported by a horizontal arm 25 integrally formed with the plate 2 below the path of travel of the strip S is the supplemental tensioning device 26. As shown, the device 26 is in the form of an upright fork with spaced tines 21 and 28 between which the binding strip S passes prior to entering between the plates 2 and 3 of the main tensioning element. The tine 21 is fixed in a collar 29 rotatably adjustable about the time 28 which, in turn, is anchored at the bottom in a lug 30 at the end of the bracket arm 25, said collar 29 being fixable in adjusted positions by a set screw 3|.

Also embodied in the tensioning means I is a guiding element '32 which is relied upon to hold the strip S to a predetermined level of travel. As shown in Fig. IV, this guide element 32 is of angle configuration with a vertical slit 33 in one of its flanges to receive the strip S and a vertical slot 34 in the other of its flanges for passage of the shank of a headed screw 35 by which it is secured with capacity for up and down adjustment to a projection 36 on the plate member 2.

Due to being constructed and arranged as described, the main and supplemental tensioning elements and the guide element are all accessible for convenience of initial insertion of the strip from above which obviously is highly advantageous in practice from the stand-point of time saving. The tensioning means of our invention is moreover advantageous in that the main and supplemental tensioning elements are separately adjustable, so that on the one hand, any desired normal tension can be predetermined for the strip, while, on the other hand, control of the strip is had during periods of release of the main tensioning element through maintenance of a lesser tension on said strip by the supplemental tensioning element.

Having thus described our invention, we claim:

1. Strip tensioning means for sewing machines, including a fixed clamp member and an opposing clamp member between which the strip is passed horizontally upright enroute to the stitch-forming instrumentalities of the sewing machine, a

,vertical arm to the upper end of which the movable clamp member is attached, means on the fixed clamp member to which the lower end of the arm is loosely connected with capacity for universal pivotal movement, a guide stem on said fixed component projecting through an opening intermediate the ends of the arm, both said pivotal connection and said stem being below the path of travel of the strip so that the clamp members are accessible from above for convenience of initially inserting the strip between them, and a helical spring in compression between a regulating nut on the outer end of the stem and the arm whereby the movable clamp member is yieldingly urged toward the fixed clamp member.

2. Strip tensioning means for sewing machines including a fixed clamp member and an opposing clamp member between which the strip is passed horizontally upright enroute to the stitch-forming instrumentalities of the sewing machine, a vertical arm to the top end of which the movable clamp member is attached, a stud projection on the fixed clamp member to which the lower end of the arm is loosely connected below the path of travel of the strip with capacity for universal pivotal movement, a spring for urging the movable clamp member toward the fixed clamp member, a cam finger fulcrumed on the pivot stud for the arm and adapted to coact with said arm to effect withdrawal of the movable clamp member away from the fixed clamp member in opposition to the spring to relieve the tension on the strip, and means for actuating the cam finger.

3. Strip tensioning means for sewing machines comprising a pair of opposing clamp elements between which the strip is passed horizontally upright enroute to the stitch-forming instrumentalities of the sewing machine, means whereby the clamp elements are connected together below the path of travel of the strip so as to be accessible from above for convenience of initially inserting the strip between them, and a slitted guide likewise open from above for determining a definite level of travel for the strip, said guide being vertically adjustable on one of said clamp members.

4. Strip tensioning means for sewing machines, including a fixed clamp member and an opposing clamp member between which the strip is passed horizontally upright enroute to the stitch-forming instrumentalities of the sewing machine, a vertical arm to the upper end of which the movable clamp member is attached, means on the fixed clamp member to which the lower end of the arm is loosely connected with capacity for universal pivotal movement, a guide stem on said fixed component projecting through an opening intermediate the ends of the arm, both said pivotal connection and said stem being below the path of travel of the strip so that the clamp members are accessible from: above for convenience of initially inserting the strip between them, a helical spring in compression between a regulating nut on the outer end of the stem and the arm whereby the movable clamp member is yieldingly urged toward the fixed clamp member, and treadle means whereby the arm may be actuated to relieve the tension on the strip or to open the clamp for initial insertion of the strip.

5. Strip tensioning means for sewing machines comprising a pair of opposing clamp elements between which the strip is passed horizontally upright enroute to the stitch-forming instrumentalities of the sewing machine, means whereby the clamp elements are connected together below the path of travel of the strip so as to be accessible from above for convenience of initially inserting the strip between them, and a slitted guide likewise open from above for determining the level of travel of the strip between the aforesaid clamp elements, said guide being secured, with capacity for vertical adjustment, to one of the clamp elements.

6. Strip tensioning means for sewing machines comprising a main tensioning device with a pair of opposing clamp members between which the strip is passed horizontally upright enroute to the stitch instrumentalities of the sewing machine, and means whereby said clamp members are yieldingly connected together below the path of travel of the strip so as to be accessible from above for convenience of initially inserting said strip between them, and a vertical fork-like supplemental tensioning device poistioned beyond the main tensioning device and likewise open from above, said supplemental device including a pair of tines whereof one is fixed in a collar which is rotatively adjustable about the other tine for the purpose of varying the tensioning induced in the strip, the last mentioned tine being supported by one of the clamp members of the main tensioning device.

7. Strip tensioning means for sewing machines comprising a main tensioning device with a pair of opposing clamp members between which the strip is passed horizontally upright enroute to the stitch instrumentalities of the sewing machine, and means whereby said clamp members are yieldingly connected together below the path of travel of the strip so as to be accessible from above for convenience of initially inserting said strip between them, a rotatively adjustable vertical fork-like supplemental tensioning device beyond the main tensioning element and likewise open from above, and an intermediately-positioned vertically-adjustable slitted guide similarly open from above for determining the level of travel of the strip through the main and supplemental tensioning device said supplemental tensioning device and guide being both supported by one of the members of the main tensioning device.

8. Strip tensioning unit for sewing machines comprising a main tensioning device and an aligned auxiliary tensioning device beyond said main tensioning device each having a pair of components between which the strip is passed horizontally upright enroute to the stitch forming instrumentalities of the sewing machine and each being accessible from above for convenience of initially threading the strip; an intermediately positioned vertically-adjustable slitted guide similarly open from above for determining the level of travel of the strip through the main and auxiliary tensioning devices; and a common support for said main and auxiliary tensioning devices and the guide, removably secured to the sewing machine.

CHARLES S. THOMPSON. FRANK A. KUCERA. ALBERT S. RIVIERE. 

